To change timeouts you need to edit common.php for your installation.

These are the fields that control timeout:
"timeoutMinutes" => 144000, //time to wait before automatic session expired, in minutes
"warningMinutes" => 2, //time to wait for warning message, after that session is expired, in minutes
"timeoutWarning" => "Your session will end in 2 minutes!", //text of expiration message
timeoutMinutes - how long system waits before showing Warning box to User.
warningMinutes - ho long Warning box lives, when time is gone, users log off

To disable timeout you need just set value like 144000, it's about 100 days.

How it works: system set session time and cookies lifetime to timeoutMinutes + warningMinutes. System set timer which checks current logined time and if that time more timoutMinutes - showes warning box. If user click on box then system reinit session with 0 minutes if not - user log off from system after timoutMinutes + warningMinutes.

Also system checks locked records and if time is up and user don't have activite then record can be locked other user.